Antenne wi-fi Définition Caracteristiques

Antenna wi-fi Defining Characteristics

DEFINITION

TheWiFi antenna is a computer accessory of the most important. It aims to achieve your WiFi network.TheWiFi antenna is defined as follows: Thewireless antenna is part of a set of walkie -Fi, or facility receiving wireless (radio), designed to radiate or receive waves wireless (radio) .
or:
TheWiFi antenna is a device for radiating or remote capture waves Fi (electromagnetic) in a device or a transmitting station and receiving wireless (eg a wireless access point)

This obliges us to give you the definition of the radio wave or rather electromagnetic

Perturbation
propagating in a medium so that at any point of this medium size used
to measure the disturbance is a function of time, while at all times,
moving at a point depends on the coordinates of this point .

or

Changing the physical state of a propagating medium following a local disturbance.

or

Oscillation, that is to say periodic variation of a physical state, which propagates in space or in matter.

An outline will be most telling:: Being the wavelength.

WiFi : Group of techniques that can wirelessly transmit data from a network using Ethernet.

Systems implemented using a frequency band located around 2.4 GHz or
2489 (GHz) and flows can vary between 2 and 54 megabits per second
(Mbps). The technology of wireless Ethernet been developed in the United
States by the WECA (Wireless Ethernet Compatibility Alliance).The work of this association that brought together several companies gave birth to standard Wi-Fi (802.11b).The abbreviation Wi-Fi is wireless fidelity.After
the huge success of this new standard, whose name was later also used
to designate the 802.11a and 802.11b, WECA in 2002 became the Wi-Fi
Alliance.

CHARACTERISTICS OF THE ANTENNA WIFI

The wifi antenna is an electrical conductor more or less complex, generally placed in an open area so that the waves WiFi can reach it without impediment ..

TheWiFi antenna is defined by the following characteristics:

Frequency of use of thewifi antenna2.4Ghz

Type ofantenna wifi

Power handling issue of thewifi antenna

Directivity, gain and radiation pattern before thewifi antenna

Size and shape of theantenna wifi

Polarization of theantenna wifi

Feeding method and feed point impedance of theantenna wifi

Strength of thewifi antenna

Shape and dimensions of theantenna wifi

The shape and dimensions of a WiFi antenna
in general is extremely variable: that of a cell phone is limited to a
small protrusion on the camera body while the parable of the radio
telescope exceeds 100 m in diameter.Very roughly we can say that for the same frequency, the dimensions of a WiFi antenna
will be even greater than his gain will be high due to the use of reflective elements, as for the dish , for example.These
antennas wifi no exception to the rule. The half-wave antenna, as its
name implies, has a length almost equal to half the wavelength at which
it was manufactured.

Thecollinear antenna is often installed on the roof.It is omnidirectional, its gain, 7 to 15 dBi, is related to its vertical dimension up to 2 meters.

These
first two descriptions, operating in bias V, can be regarded as
antennas or docking base as compatible with a 360 ° environment.

Ex directional antennas: Yagi

Theantenna panel may be an internal network ofquad antenna orpatch antenna, or an array of dipoles.Begins to gain 8 dBi (8 × 8 cm) to achieve 21 dBi (45 × 45 × 4.5 cm).It's the antenna that provides the best value gain / bulk and also the best performance, which is around 85 to 90%.
Beyond this maximum gain, it is no longer manufactured, problems arise
because of coupling (losses) between the dipoles and floors should also
consider doubling the surface.The volume of a panel antenna is minimal.

The antenna type dish
solid or perforated (mesh).His interest in employment lies in the pursuit of profit obtained from a theoretical diameter of approach as follows:

18 dBi = 46 cm,

19 dBi = 52 cm,

20 dBi = 58 cm,

21 dBi = 65 cm,

22 dBi = 73 cm,

23 dBi = 82 cm,

24 dBi = 92 cm,

25 dBi = 103 cm,

26 dBi = 115 cm,

27 dBi = 130 cm,

28 dBi = 145 cm,

29 dBi = 163 cm,

30 dBi = 183 cm.

The yield of the dish is average, 45 ~55%.The volume of the antenna, which takes account of the hinge, so the focusis significant.

Antenna selection

Gain antennas are omni-directional or intended for "longer range" as possible, a few kilometers.

The
panels and parabolic antennas are directional only, that is to say they
favor a preferred direction (more or less open) at the expense of other
undesirable.

It
finds that the panel antennas are often preferred (even better) when
the link budget is favorable, but as soon as the system must be more
efficient, the parables are required.The balance point at 21 dBi, is done with a square of side panel 45 cm and the other a dish d = 65 cm.

In
conclusion, directional, or point to point, it is interesting to equip
themselves with a first panel and, if circumstances require, a parable.

The Wi-Fi antennas are usually equipped with SMA, RP-SMA or N according to the manufacturer.However, the antenna gain (in dBi or dBd) used to broadcast (receive free) must comply with regulations EIRP (Equivalent Isotropic Radiated Power).